Mac Book Pro13" 2017 Could not install bootloader

Hi there, welcome to the forum!
There are several users in the forum with a MacBookPro, but there are so different models that your issue might be peculiar.
Your error reminds me of this thread (although that was a Macbook Air):

The solution might seem a bit strange and complicated, but it’s worth trying in my opinion.
Before doing that, if you want, I remember also an interesting suggestion from a topic which was going on in parallel in those days (for a MacBook Air again…):

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